In systems that are disclosed, for example, in DE 10 2005 014 897, EP 0 858 929 A1, and DE 10 2004 007 325 B3, it must be ensured that the two connectors are disposed in a predefined rotational position with respect to their joining direction, the direction in which the connectors have to be moved relatively toward each other to join them together, or with respect to the central longitudinal axis of the free end of the holding rod that supports one connector. The connectors must therefore be positioned in a predefined rotational position on the holding rod, on a guide component which receives the holding rod and is disposed in the backrest, or on another component. This rotational positioning requirement increases the costs of production and assembly and involves the risk of a defective assembly.